Car radios in general are adapted to be tuned manually and automatically. Manual tuning operation is effected by manually turning a tuning knob whilst automatic tuning operation is effected by merely pushing a pushbutton to which a desired broadcasting station is previously reserved. To preset a desired frequency to a pushbutton, the manual tuning knob is operated to bring a memory slide plate to a position corresponding to a desired frequency and thereafter fix a positional relation between the memory slide plate and a frequency setting plate linked to the pushbutton. Therefore, the tuning knob is used for both the manual and automatic tuning operations. The rotation of the manual tuning knob is transmitted to the memory slide plate via a clutch mechanism and further to a tuning circuit element and is therein converted to an energy for changing its constant.
Such clutch mechanism 5 as shown in FIG. 10A consists of an idler gear 10 and a wheel gear 11 engageable therewith, for example, and the idler gear 10 is shifted by a lever 4 away from the wheel gear 11 when a pushbutton 1 is pushed so that the rotation of the manual tuning knob is not conveyed to the tuning circuit element 15.
FIG. 1 schematically shows a series of constituents relating to such automatic tuning operation. When the pushbutton 1 to which a desired frequency is preset is pushed in, the movement is transmitted to the clutch mechanism 5 via an arm 2, link 3, and clutch lever 4. With this movement, the clutch mechanism operates so as not to convey a rotation of the manual tuning knob to the tuning circuit element 15. On the other hand, the memory slide plate 16 is brought to a position corresponding to the preset frequency by the pushbutton 1 and this displacement is transmitted to the tuning circuit element 15 to have it select the preset frequency.
In the prior art, however, to assemble the clutch mechanism in a tuner, both a clutch base plate and a clutch plate of the clutch mechanism must be fixed to a frame of the tuner by means of plural bolts. This disturbs laboursaving and automation of its assembly.